Goals
Run a 'proper' storage server OS
Migrate to more reliable RAID configuration
Upgrade storage capacity (expect to run out in March 2018)
Backup data
Support 6k video editing across a team of 12
Adding 10Gbps to server
Adding 10Gbps switch
Adding 10Gbps to clients

You can use any existing server you have, but get a decent RAID card, such as a H830 2GB nvcache.
Go to xbyte.com, and price out something like a Dell MD1400. You could build something nice with a bunch of NL SAS drives. This whole thing will run at 12gbps bandwidth. Hook your server up to 10gbps fiber switch.

It'll look like this:

client -> fiber switch -> server -> 12gbps SAS to MD1400 (and back)

You could probably do the whole thing for under 7k depending on how big the hard drives are and how many. If you threw in 12x 4TB NL SAS drives, it'll be under 7k most likely. You could RAID10 that.

@scottalanmiller If you were building storage at the scale of something like a Backblaze pod, how would you do it?

Seems like I asked this one time before, but I forget.

You wouldn't, it's that simple. The BB Pod is just one tiny piece of a giant cluster. It only works as it is because it's a disposal cog in a bigger machine. If you wanted just "a pod", you just... don't. It's a dumb idea. You should never have a single point of failure that freaking large. It is too much to back up and restore all at once.

You'd build a cluster of smaller storage devices, not a single monolithic one.

@scottalanmiller If you were building storage at the scale of something like a Backblaze pod, how would you do it?

Seems like I asked this one time before, but I forget.

You wouldn't, it's that simple. The BB Pod is just one tiny piece of a giant cluster. It only works as it is because it's a disposal cog in a bigger machine. If you wanted just "a pod", you just... don't. It's a dumb idea. You should never have a single point of failure that freaking large. It is too much to back up and restore all at once.

You'd build a cluster of smaller storage devices, not a single monolithic one.

So essentially, you are saying that unless you're doing something like Backblaze, there's no real reason to build something like this?

@scottalanmiller If you were building storage at the scale of something like a Backblaze pod, how would you do it?

Seems like I asked this one time before, but I forget.

You wouldn't, it's that simple. The BB Pod is just one tiny piece of a giant cluster. It only works as it is because it's a disposal cog in a bigger machine. If you wanted just "a pod", you just... don't. It's a dumb idea. You should never have a single point of failure that freaking large. It is too much to back up and restore all at once.

You'd build a cluster of smaller storage devices, not a single monolithic one.

So essentially, you are saying that unless you're doing something like Backblaze, there's no real reason to build something like this?

That's what I've been saying for years. The BB Pod is an extremely specific purpose designed component of a larger system that has no reason to exist outside of that larger purpose. It is of zero value to anyone not using it for the purpose for which it is designed.

It's like looking at a 100TB RAID array of RAID 10 x 20 10TB drives and asking how to use a single 10TB drive without RAID in a server. Of course, the answer is you never do that. The 10TB SATA drives only make sense to use in production when part of the RAID 10 array. Remove the array, you remove their applicability. Same here. You can't just pull one cog out of a machine and wonder where to use it, it doesn't work that way.

Goals
Run a 'proper' storage server OS
Migrate to more reliable RAID configuration
Upgrade storage capacity (expect to run out in March 2018)

FreeBSD, RAIDZ2 single array. With combined arrays you'd be faster than the single, with RAID 6 you'll have more protection that the two RAID 5s. Capacity will be the same. Or buy a few more drives and go to RAIDZ3 right away.